A semiconductor wafer, also referred to as wafer, is usually used for fabricating semiconductor circuits. The wafer is subjected to a number of processing steps in order to form the semiconductor circuits.
After all the processing steps have been carried out, the wafer contains a large number of semiconductor circuits of identical type. These semiconductor circuits are arranged in rows and columns. The rows run in a first direction and the columns run in a second direction running transversely with respect to the first direction. The semiconductor circuits of a row are arranged at regular intervals along the first direction. The semiconductor circuits of a column are arranged at regular intervals along the second direction. The wafer contains a two-dimensional array of semiconductor circuits.
As illustrated in U.S. Pat. No. 5,838,163, which is incorporated herein by reference, by way of example, a wafer additionally comprises first sawing regions, which extend over the wafer in the first direction, and second sawing regions, which extend over the wafer in the second direction and cross the first sawing regions. A respective one of the semiconductor circuits is arranged between respective adjacent first sawing regions and respective adjacent second sawing regions. The first sawing regions and the second sawing regions together form the sawing frame or scribing frame, which is also referred to as kerf.
For singulating the semiconductor circuits, the wafer is sawn up along separating regions, which in each case run within a first sawing region or within a second sawing region through the wafer. A large part of the sawing frame is thus destroyed during the singulation of the semiconductor circuits.
Test structures are often formed within the sawing frame, for example additional semiconductor components or semiconductor circuits. Measurements are carried out on the test structures during the fabrication of the wafer. For making contact with the test structures, connection contacts that are conductively connected to the test structures are formed in the sawing frame. By way of example, U.S. Pat. No. 5,059,899, which is incorporated herein by reference, describes test circuits arranged in the sawing frame and connection contacts connected to the test circuits.
U.S. Patent Application Publication No. 2003/0034558 A1, which is incorporated herein by reference, describes an arrangement of test structures for identifying latent defects of a multilayer wiring structure that is formed on a semiconductor wafer. The test structures are arranged within sawing regions running along a first direction. One portion of the test structures is arranged in a first row, and a further portion of the test structures is arranged in a second row, the first row and the second row being offset along a second direction running transversely with respect to the first direction. First connection elements and second connection elements of individual test structures are arranged offset.
U.S. Patent Application Publication No. 2003/0006795 A1, which is incorporated herein by reference, describes test element groups (TEG) arranged in sawing regions of a semiconductor substrate. The TEGs are arranged between guard bands (GB). Each individual TEG comprises a respective source, drain and gate contact. The source, drain and gate contacts are arranged in a respective row running along the GBs, the row in which the gate contacts are arranged being offset along a second direction, which runs transversely with respect to the direction prescribed by the GBs, relative to the rows in which the source and drain contacts are arranged.
U.S. Patent Application Publication No. 2001/0035762 A1, which is incorporated herein by reference, discloses an arrangement of MIS transistors arranged in sawing regions of a semiconductor wafer. Each MIS transistor comprises source, drain and gate contacts, the source and drain contacts being arranged in a first row running along a first direction, and the gate contacts being arranged in a second row running along the first row, and the second row being offset along a second direction running transversely with respect to the first direction.
U.S. Pat. No. 6,124,143, which is incorporated herein by reference, describes an arrangement of a process monitoring construction, in which bonding pads are arranged at the periphery of an integrated circuit. Sawing regions are arranged between the bonding pads of adjacent integrated circuits, supplementary metal lines that are used for test purposes running between the bonding pads and the sawing regions. The supplementary metal lines are connected to a process monitor situated on the integrated circuit.
U.S. Pat. No. 6,177,733 B1, which is incorporated herein by reference, describes a test arrangement in which five electrode pads are arranged in such a way that four of the electrode pads form a rectangle and the fifth electrode pad is situated in the center of the rectangle. A multiplicity of semiconductor elements are arranged between the electrode pads and connected to each of the five electrode pads.
U.S. Pat. No. 5,923,047, which is incorporated herein by reference, describes an arrangement of test pads arranged in sawing regions of a semiconductor wafer. A first portion of the test pads is arranged in a row running along a sawing region. A further portion of the test pads is arranged in a row likewise running along the sawing region, the second row being offset along a direction running transversely with respect to the direction of the sawing region. Each test pad is connected to a respective pad situated on a chip.
U.S. Pat. No. 5,627,101, which is incorporated herein by reference, describes test structures arranged in sawing regions of a wafer. The test structures in each case have two first pads—arranged in a first row running along a first direction—for applying a current to the test structure. Furthermore, the test structure comprises two second pads for measuring a voltage, which are arranged in a second row, which runs along the first direction, and in the case of which a connection contact of the first row and a connection contact of the second row have edges that overlap as seen in the first direction.
Contact is made with the test structures by placing test needles of a needle card onto the connection contacts. The test needles are usually arranged in a row on the needle card. The tips of two adjacent test needles in each case have a standard spacing of 80 μm. The connection contacts in the sawing frame are likewise arranged in a row. In this case, a longitudinal direction of the row runs along the first direction or along the second direction of the sawing regions. The front edges—relative to the longitudinal direction—of adjacent connection contacts in each case have the same spacing as the tips of adjacent test needles.
The area of the sawing region is always chosen to be as small as possible in order to make as much area of the wafer as possible available for the semiconductor circuits of the chips. Nevertheless, as many test structures and connection contacts for making contact with the test structures as possible are to be arranged in the sawing region. In this case, the area requirement for the connection contacts is usually higher than the area requirement for the test structures.
During the measurement of an electrical parameter, a predetermined current flows through the cross-sectional area of a test needle. A heating of the test needle is dependent on the current density relative to the cross-sectional area. A test needle with a smaller cross-sectional area is, therefore, heated to a greater extent by the same current than a test needle with a larger cross-sectional area. This means that the cross-sectional area of the test needle cannot be reduced all that much if excessively great heating of the test needle is to be avoided.
The connection contacts are compressed into their width somewhat upon placement of the test needles. This means that the distance between mutually facing edges of adjacent connection contacts cannot be reduced all that much if a short circuit of the adjacent connection contacts upon placement of the test needles is to be avoided.